Field of the Invention
The present disclosure relates to an image processing apparatus, and more specifically to an image processing apparatus that acquires a tomographic image of a subject based on a series of transparent images captured while synchronously moving a radiation source and a FPD (flat panel-type X-ray detector) in opposite directions with each other, and also relates to a radiation tomography apparatus equipped with the image processing apparatus and a method of performing image processing.
Description of the Related Art
The following description of related art sets forth the inventors' knowledge of related art and certain problems therein and should not be construed as an admission of knowledge in the prior art.
In medical institutions, as shown in FIG. 22, a radiographic apparatus 51 for acquiring a tomographic image of a subject may be used. In some radiographic apparatuses 51 of this kind, the apparatus is structured to acquire a tomographic image by superimposing a series of transparent images consecutively captured while synchronously moving a radiation source 53 for irradiating radiation and an FPD 54 for detecting the radiation. In such a radiographic apparatus 51, during the capturing of a series of transparent images, the radiation source 53 and the FPD 54 move so as to approach with each other in a body axis direction of the subject. After the position of the radiation source 53 and that of the FPD 54 in the body axis direction coincide, the radiation source 53 and the FPD 54 move so as to distance themselves with respect to each other in the body axis direction. Such a radiographic apparatus is disclosed, for example, in Patent Document 1 (see. e.g., International Publication No. WO2011/086604).
The operation of capturing a tomographic image mentioned above by the radiographic apparatus 51 will be explained. Initially, the radiation source 53 irradiates radiation intermittently while moving. For example, every time one irradiation is completed, the radiation source 53 moves in the body axis direction of the subject and again irradiates radiation. Thus, a total number of pieces of transparent images (e.g., 74) are acquired, and superimposed. The completed image is a tomographic image in which a tomogram acquired by cutting the subject at a certain cutting plane is seen.
However, conventional technologies as mentioned above have certain problems. For example, in the conventional radiographic apparatus 51, disturbance of images often occurs at the end sections of the tomographic image.
A transparent image is acquired while moving the X-ray tube 53 and the FPD 54 with respect to the object, and therefore the position where the subject is seen differs in each transparent image. Accordingly, the image of the subject seen in an end section of a certain transparent image is not seen in another transparent image. However, such a situation will not be considered at the time of generating a tomographic image D. For example, a tomographic image D is generated on the assumption that images of the subject required for reconstruction are all contained in the transparent image.
Then, at the end section of the tomographic image D to be generated, an image of the subject that may be required to generate a tomographic image D may be missing. Such lacking of an image shows up as a false image in a tomographic image D. More concretely, as shown in FIG. 23, the image may be disturbed notably at both sections of the tomographic image D in the moving direction of the FPD 54 and the radiation source 53.
Under the circumstances, in a conventional structure, by compensating the lack of images to generate a tomographic image, attempts may be made to enhance the visibility of the tomographic image. One method is to compensate for the lack of images by extending the transparent image by repeatedly pasting the pattern of the end section of the transparent image. However, it cannot be said that sufficient image extrapolation is performed in this method. In detail, in the aforementioned method, since an end section of the image is simply pasted without considering the image of the subject to be seen in the image, as shown in FIG. 24, joined images of the subject may become discontinuous. Thus, in some cases, the end section of the image becomes more unnatural by the extrapolation processing. Under the circumstances, in a conventional method, the visibility of the tomographic image may deteriorate more than generating a tomographic image without performing extrapolation.
The description herein of advantages and disadvantages of various features, embodiments, methods, and apparatus disclosed in other publications is in no way intended to limit the present invention. For example, certain features of the described embodiments of the invention may be capable of overcoming certain disadvantages and/or providing certain advantages, such as, e.g., disadvantages and/or advantages discussed herein, while retaining some or all of the features, embodiments, methods, and apparatus disclosed therein.